Hinge device

ABSTRACT

A hinge device of a portable terminal connects a keyboard member to a comparatively massive display member and has cam and friction mechanisms. The cam mechanism has a fixing cam for axially receiving a shaft which extends into a cam case having a rotation arresting mechanism fixed on the shaft, a slider cam provided slidably in a manner to confront the fixing cam restrained in its rotation by the cam case, and an elastic mechanism for pressing the slider cam toward the fixing cam. The friction mechanism has a friction ring attached to the shaft and fitted into the friction case under pressure with a rotatable rotation arresting mechanism, so that both of automatic close lock function from a predetermined closed angle between the first and second members and a free stop function when opening and closing operation of the first and second members can be realized together without strain.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional of application Ser. No. 10/746,580 filed Dec. 24,2003 which is incorporated here by reference, and which claimed priorityon Japanese Patent Application No. 2002-375954 filed Dec. 26, 2002,which claim is repeated here.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hinge device used for a portableintelligence terminal structured with a first member composed of akeyboard main body and a second member composed of a display device, inparticular, suitable for use in connecting the second member, which iscomparatively massive at a portion of the display device, to the firstmember in a openable and closable manner relatively.

2. Description of the Relevant Art

Conventionally, as this kind of a hinge device, a technology disclosedin a Japanese Patent Laid-open No. 2000-337008 is well-known.

A hinge device disclosed in this laid-open patent official gazetteincludes: a shaft having an arresting portion at an end portion; a casebody having a rotation arresting means allowing the shaft to be insertedthrough axially at the central portion and to be arrested at anarresting portion; a slider cam slidably arrested in a key grooveprovided on an open end side of the case body in the axial direction andhaving a cam portion at one end, and at the same time, allowing theshaft to be inserted through axially at the central portion; a fixingcam having a cam portion at an end confronting to the cam portion of theslider cam and allowing the shaft to be inserted through axially at thecentral portion; and a compression spring rounded around the shaft,being accommodated in the case body, and installed resiliently betweenthe case body and the slider cam.

SUMMARY OF THE INVENTION

Since a purpose of a hinge device shown in the laid-open patent officialgazette is to control an opening-and-closing operation of the displaydevice, being the second member, to the keyboard main body, being thefirst member, only with a cam mechanism, there arises a disadvantagethat even for a compact type portable intelligence terminal having acomparatively massive display device, being the second member, it isdifficult to realize both an automatic closed lock function from apredetermined closed angle, and a free-stop function at the time ofopening and closing operation with regard to the keyboard main body,being the first member, of the display device.

An object of the present invention is to provide a hinge device for aportable intelligence terminal which can realize both an automaticclosed lock function from a predetermined closed angle and a free-stopfunction at the time of opening and closing operation at the same timewith a structure as simple as possible, when an opening and closingoperation of a display device, which is comparatively massive secondmember, is conducted with regard to a keyboard main body, being thefirst member.

In order to achieve the object described above, the present inventiondiscloses a hinge device connecting a first member and a second memberbeing opened and closed relatively, provided with a cam mechanism and afriction mechanism disposed on a shaft coaxially, wherein the cammechanism includes a fixing cam provided by allowing a shaft to insertthrough axially at each central portion into a cam case side having arotation arresting means fixed on the shaft, a slider cam providedslidably in a manner to confront to the fixing cam, being restrained itsrotation by the cam case, and an elastic means to press the slider camtoward the fixing cam side; wherein the friction mechanism includes: afriction case having a rotation arresting means attached to the shaft ina manner to be rotatable, and a friction ring attached to the shaft andfitted in the friction case with pressure.

The present invention further discloses a hinge device connecting afirst member and a second member being opened and closed relatively,provided with a cam mechanism and a friction mechanism disposed on ashaft coaxially; wherein the cam mechanism includes a fixing camprovided by allowing a shaft to insert through axially at each centralportion into a cam case side having a rotation

-   -   arresting means fixed on the shaft, a slider cam provided        slidably in a manner to confront to the fixing cam, being        restrained its rotation by the cam case, and an elastic means to        press the slider cam toward the fixing cam side;    -   wherein the friction mechanism includes a flange portion        provided on the shaft, a bracket attached on the shaft, a        friction washer, an elastic means, and a clamping nut so that        friction torque is generated there between the friction washer        and one side or both sides of the bracket.

At that time, the clamping nut can be replaced by caulking an endportion of the shaft.

The present invention still further disclose a hinge device connecting afirst member and a second member being opened and closed relatively,having a pair of cam mechanism disposed on a shaft coaxially on theshaft, wherein each cam mechanism includes a fixing cam provided byallowing a shaft to insert through axially at each central portion intoa cam case side having a rotation arresting means fixed on the shaft, aslider cam provided slidably in a manner to confront to the fixing cam,being restrained its rotation by the cam case, and an elastic means topress the slider cam toward the fixing cam side.

In any case of the invention described above, at least one portion ofeach cam portion provided on the fixing cam and the slider cam of eachcam mechanism is formed in a plane portion so that friction torque isgenerated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a keyboard main body which is a first memberand a display device which is a second member of a portable intelligenceterminal using a hinge device relating to the present invention, bothbeing seen in a open state;

FIG. 2 is a front view of the hinge device relating to the presentinvention;

FIG. 3 is a right side view of the hinge device shown in FIG. 2;

FIG. 4 is a left side view of the hinge device shown in FIG. 2;

FIG. 5 is a front sectional view of the hinge device shown in FIG. 2;

FIG. 6 is a right side view of a fixing cam of the hinge device shown inFIG. 2;

FIG. 7 is a front view of the fixing cam of the hinge device shown inFIG. 2;

FIG. 8 is a plane view of the fixing cam of the hinge device shown inFIG. 2;

FIG. 9 is a left side view of a slider cam of the hinge device shown inFIG. 2;

FIG. 10 is a right side view of the slider cam of the hinge device shownin FIG. 2;

FIG. 11 is a plane view of the slider cam of the hinge device shown inFIG. 2;

FIG. 12 is a vertical cross section of the slider cam of the hingedevice shown in FIG. 2;

FIG. 13 is a side view of the cam guide shown in FIG. 2;

FIG. 14 is a vertical cross section to explain movement of the hingedevice shown in FIG. 2 to FIG. 5;

FIG. 15 is an explanatory view to explain movement of each cam portion;

FIG. 16 is a front view showing other embodiment of the hinge devicerelating to the present invention;

FIG. 17 is a right side view of the hinge device shown in FIG. 16;

FIG. 18 is a left side view of the hinge device shown in FIG. 16;

FIG. 19 is a vertical cross section of the hinge device shown in FIG.16;

FIG. 20 is a right side view of a shaft used in the hinge device shownin FIG. 16;

FIG. 21 is a side view of a bracket used in the hinge device shown inFIG. 16;

FIG. 22 is a side view of a cam guide used in the hinge device shown inFIG. 16;

FIG. 23 is a left side view of a first friction washer used in the hingedevice shown in FIG. 16;

FIG. 24 is a left side view of a second friction washer used in thehinge device shown in FIG. 16;

FIG. 25 is a side view of a retaining washer used in the hinge deviceshown in FIG. 16;

FIG. 26 is an explanatory view to explain operation of the hinge deviceshown in FIG. 16;

FIG. 27 is a front view showing a still another embodiment of the hingedevice;

FIG. 28 is a right side view of the hinge device shown in FIG. 27;

FIG. 29 is a left side view of the hinge device shown in FIG. 27;

FIG. 30 is a vertical cross section of the hinge device shown in FIG.27; and

FIG. 31 is a vertical cross section to explain operation of the hingedevice shown in FIG. 27.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Drawings show an embodiment of the present invention. In FIG. 1, the oneshown with a reference number 1 denotes, for instance, a portableintelligence terminal, and the one shown with a reference number 2denotes a keyboard main body forming a first member. The one shown in areference number 3 denotes a display device composed of, for instance, aliquid crystal display device which forms a second member.

The hinge devices A and A relating to the present invention are used forconnecting the keyboard main body 2, being the first member, and thedisplay device 3, being the second member, so that the key board maindevice and the display device can open and close relatively to eachother, and installed between attachment portions 2 a and 2 a of thekeyboard main body 2 and attachment portions 3 a and 3 a of the displaydevice. Though the hinge devices A and A are provided in a pair in thisdrawing, they can be in one piece. Since the hinge devices A and A arebilaterally symmetrical, and they are structured in the same way, theexplanation thereof will be made hereinafter for a left hinge device Ain FIG. 1.

The structure of a cam mechanism 4 affected by an elastic means is asfollows. Firstly, in FIG. 2, the one shown with a reference number 5denotes a shaft, and a reference number 6 denotes a cam case. The camcase 6 opens at one end, having rotation arresting means 6 a and 6 aformed of a pair of concave grooves axially on the periphery, and adeformed attachment portion 5 a provided at one end of the shaft 5 isallowed to insert through into a deformed attachment hole 6 c providedon the side wall 6 b and engaged therewith, and fixed to the shaft 5 soas to be rotated with the shaft 5 by a fixing pin 7.

On the open end side of the cam case 6, a slider cam 8 is slidablyaccommodated axially, being restrained its rotation by the cam case 8,while allowing the shaft 5 to insert through into a through hole 8 aprovided oxially at the central portion, and allowing a pair of keyportions 8 b and 8 b provided on the outside thereof to engage with akey grooves 6 d and 6 d provided on the periphery of the cam case 6. Anelastic means 9 composed of a compression spring wound around the shaft5 is disposed between the slider cam 8 and the side wall 6 b of the camcase 6.

A fixing cam 10 is disposed at a position confronting to the slider cam8, allowing the shaft 5 to insert through into a through hole 10 aprovided axially at the central portion, the fixing cam 10 is locked atone side of a flange portion 11 a of a friction ring attachment portion11 in a friction mechanism, to be described later, which is provided onone side of the shaft 5, and is in a state that its rotation isrestricted by a cam guide 12 having a rotation arresting means 12 bwhich has a flat portion on the outside thereof. A method of arrestingthe rotation of the fixing cam 10 at the cam guide 12 is conducted byengaging a concave groove 10 b of the fixing cam 10 inserted into adeformed attachment hole 12 a with a convex portion 12 c of the deformedattachment hole 12 a provided on the cam guide 12, but it is not limitedto this method.

On the confronting faces of the slider cam 8 and the fixing cam 10, camportions 13 and 14 composed of convex portions 13 a and 14 a, andconcave portions 13 b and 14 b whose respective upper surfaces are flat,are disposed.

A structure of a friction mechanism 15 is as follows. A reference number16 denotes a friction case which has a side wall 16 a, opens at one end,and is provided with a rotation arresting means 16 b composed of a flatportion on the outer periphery. A shaft 5 is inserted axially at thecentral portion of the friction case 16, and rotatably supported in athrough hole 16 c provided on the side wall 16 a. The friction case 16is locked at the shaft 5 by the E ring 5 c attached to on the other endportion of the shaft so as not to be got out. In the inside of thefriction case 16, a friction torque generation hole 16 d is providedconcentrically with a through hole 16 c, and in this friction torquegeneration hole 16 d, three pieces of friction rings 17 made of, forinstance, rubber, is press fitted to the friction ring attachmentportion 11 between the flange portions 5 b, 5 b formed to the shaft 5.Incidentally, though not shown, between the friction ring 17 and thefriction torque generation hole 16 d, viscous lubricant oil, forinstance, silicone oil, is applied.

Therefore, as shown in FIG. 1, FIG. 4, and FIG. 14, the cam case 6 ofthe hinge device A is allowed to insert through into and engage with thedeformed attachment hole 3 b provided on the attachment portion 3 a ofthe display device 3, and the friction case 16 is inserted into andlocked at the deformed attachment hole 2 b provided on the attachmentportion 2 a of the keyboard main body 2 to complete assembling to thehinge device A.

As shown in FIG. 4, in a closed state of the display device 3, being thesecond member, into the keyboard main body 2, being the first member,the convex portion 13 d of the cam portion 13 in the slider cam 8 is ina state of sliding down to the middle in the concave portion 14 b of thecam portion 14 in the fixing cam 10, as shown in FIG. 15. When thedisplay device 3 being the second member, is opened in relation to thekeyboard main body 2 being the first member from this state, the camcase 6 rotates together with the display device 3. At first, the convexportion 13 a of the cam portion 13 in the slider cam 8 rotating togetherwith the cam case 6 meets with resistance at the time of getting outfrom the concave portion 14 b of the cam portion 14 of the fixing cam 10in the compression spring 9, and then, as shown with a solid line and animaginary line in FIG; 15, the convex portions 13 a and 14 a ofrespective cam portions 13 and 14, on the surfaces of which are flat,slide on each other in a pressure contact state. Accordingly, byfriction torque generated from a pressure contact force betweenrespective convex portions 13 a and 14 a of these respective camportions 13 and 14, and friction torque generated between an outerperiphery of the friction ring 17 in the friction mechanism 15 and innerperiphery of the friction torque generation hole 16 d, the displaydevice 3 opens in a free-stop state to the keyboard main body 2. FIG. 14shows a state that the display device 3 is opened at 90° with regard tothe keyboard main body 2. When exceeded an open angle of about 1100 withregard to the key board main body 2, at which angle the display device 2is often opened, the display device 3 is opened only with frictiontorque of the friction mechanism 15 by sliding down of the convexportion 13 a of the cam portion 13 in the slider cam 8 into the concaveportion 14 b of the cam portion 14 in the fixing cam 10.

As for the case that an opened display device 3 is closed with regard tothe keyboard main body 2, when the display device 3 is opened at anangle of 110° or more, the convex portion 13 a of the cam portion 13 inthe slider cam 8 meets with some resistance at the time of getting outfrom the concave portion 14 b of the cam portion 14 in the fixing cam10. However, from an angle of 110°, the display device 3 is closed withregard to the keyboard main body 2 in a free-stop state, due to asynergistic effect of friction torque generated from a state of pressurecontact of respective convex portions 13 a and 14 a of respective camportions 13 and 14 and friction torque of the friction mechanism 15 asshown in FIG. 15 with a solid line and an imaginary line.

From an angle of about 10° just before the display device 3 is closed,since the convex portion 13 a of the cam portion 13 in the slider cam 8slides down from the convex 14 a of the cam portion 14 in the fixing cam10 into the concave portion 14 b, the display device 3 is automaticallyclosed, and locked not to open naturally in a closed state by a suctionforce generated at that time.

Thus, the hinge device of this embodiment locks the display device 3 ina closed state with regard to the keyboard main body 2, can open to ausage angle in a free-stop state, and at the usage angle, while thedisplay device is kept stably, it can be closed as if it were inhaledjust before closing of the display device 3 by the cam mechanism 4. Atthe time of opening and closing operation of the display device 3, asoft opening and closing feeling is given to an operator by the frictionmechanism, and a buffering effect at the time of closing can berealized.

FIG. 16 to FIG. 26 show another embodiment. According to the drawings, ahinge device B relating to this embodiment is shown as a left side onein FIG. 1, a cam mechanism 21 and a friction mechanism 22 are providedon the left and right of a flange portion 20 a provided approximately inthe central portion of a shaft 20. Since the structure of the cammechanism 21 is the same as that in the previous embodiment, theexplanation thereof will be omitted. The friction mechanism 22 isprovided on the left side of the flange portion 20 a of the shaft 20,and as shown in FIG. 21, FIG. 23 to FIG. 25, includes a first frictionwasher 23, a bracket 24, a second friction washer 25, a spring washer26, a retaining washer 27, and a clamping nut 28 from an adjacent sideof the flange portion, disposed in a manner to allow the shaft to insertthrough the through holes 23 a, 24 a, 25 a, 26 a and 27 a providedaxially at respective central portions. The first friction washer 23 isfixed to the shaft 20 by engaging an arresting piece 23 b which is bentfrom its outer periphery with an arresting groove 20 b provided on theflange portion 20 a. The bracket 24 is rotatable to the shaft 20, but arotation arresting means 24 b formed of a flat portion is provided onthe outer periphery thereof. The second friction washer 25 is structuredto rotate with the bracket 24 by engaging an arresting piece 25 b whichis bent from its outer periphery with an arresting groove 24 c providedon the outer periphery of the bracket 24. The spring washer 26 and theretaining washer 27 are restrained their rotation by the shaft 20 byallowing respective deformed through holes 26 a and 27 a to insertthrough and engage with a deformed portion 20 c of the shaft 20. Theclamping nut 28 is screwed on a male screw portion 20 d of the shaft 20,so that it is structured to generate friction torque accompanied byrotational movement of the shaft 20 by pressure contact of the firstfriction washer 23 to one side of the bracket 24, and by pressurecontact of the second friction washer 25 to the side face of the springwasher 26.

Therefore, a portion of the friction mechanism 22 is allowed to insertinto the deformed attachment hole 2 b provided on the attachment portion2 a of the keyboard main body, being the first member, the cam guide 12and the bracket 24 are engaged with the deformed attachment hole 2 b,and then a portion of the cam case 6 is allowed to insert and lock atthe deformed attachment hole 3 b provided on the attachment portion 3 aof the display device 3, being the second member, thereby assembling ofthe hinge device B is completed.

FIG. 19 shows this state in a vertical cross section. In this state, asshown in FIG. 15 with a solid line, the convex portion 13 a of the camportion 13 in the slider cam 8, inserts into the concave portion 14 b ofthe cam portion 14 in the fixing cam 10 to lock the display device 3 notto open naturally with regard to the keyboard main body 2.

When the display device 3 opens with regard to the keyboard main body 2from this closed state, since the cam case 6 rotates together with theshaft 20 and the slider cam 8 as shown in FIG. 15 with a solid line andan imaginary line, friction torque by sliding in pressure contact of aflat convex portion 13 a of the cam portion 13 in the slider cam 8 witha flat convex portion 14 a of the cam portion 14 in the fixing cam 10,and friction torque by sliding in pressure contact between the firstfriction torque 23 and the bracket 24, and between the second frictionwasher 25 and the spring washer 26, are generated, the display device 3is suspended and kept stably, especially at an open angle of about 100°to 110°, which is the usage angle. It is of course possible to openfurther to 180°, and the friction torque at that time can be freelyselected.

Subsequently, when the display device 3 is closed, at about 10° which isa closed position, owing to the rotary torque generated when the convexportion 13 a of the cam portion 13 in the slider cam 8 fits in theconcave portion 14 b of the cam portion 14 in the fixing cam 10, thedisplay device 3 is closed as if being inhaled and locked in a closedstate.

It should be noted that on which face of the first friction washer orthe second friction washer should the friction torque of the frictionmechanism 22 be generated can be freely selected other than that in theembodiment and the clamping nut 28 can be replaced by caulking of theend portion of the shaft 20.

FIG. 27 to FIG. 30 show another embodiment of a hinge device C relatingto the present invention. The hinge device C of the present embodimentis the one shown on the right in FIG. 1, and the hinge device C isprovided with bilaterally symmetrical first cam mechanism 31 and asecond cam mechanism 32 on both sides of the shaft, and the structure ofthe first cam mechanism 31 and the second cam mechanism 32 are the sameas that of the cam mechanism 4 and 21 in the previous embodiment. Atnearly the central portion of a shaft 30, a pair of a first fixing cam33 and a second fixing cam 34 allow the shaft 30 to insert through intothrough holes 33 a and 34 a provided axially at the central portion sothat respective side faces are allowed into contact impactedly with eachother, and a first cam guide 36 and a second cam guide 37 havingrotation arresting means 36 b and 37 b composed of a flat portion on theouter periphery while accommodating the first fixing cam 33 and thesecond fixing cam 34 in the inside.

On the one of both end portions of the shaft 30, a first cam case 38with an open end and provided with a rotation arresting means 38 ahaving a concave groove on the periphery is arranged allowing the shaft30 to insert through inside in the axial direction, and a deformedportion 30 a provided on an end of the shaft 30 is allowed to insertinto a deformed through hole 38 c provided on a side wall 38 b of thefirst cam case 38 and fixed so that the shaft 30 is arrested with aattachment pin in order not to get out.

On the other end of both end portions of the shaft 30, a second cam case40 with an open end is arranged allowing the shaft 30 to insert throughinside in the axial direction similarly, and the shaft 30 is allowed toinsert into a through hole 40 b provided on a side wall 40 a, so thatthe shaft 30 is arrested with a deformed flange portion 30 b in ordernot to get out while the deformed flange portion 30 b is engaged into adeformed hole.

On an aperture sides in the first and second cam cases 38 and 40, a pairof first slider cam 41 and second slider cam 42 are provided confrontingto the first and second fixing cam 33 and 34, allowing the shaft 30 toinsert through into through holes 41 a and 42 a provided axially at thecentral portion, a first and second elastic means 43 and 44 allowing towind around the shaft 30, composed of a compression spring are disposedbetween respective first and second slider cams 41 and 42, andrespective side walls 38 b and 40 a of the first and second cam cases 38and 40, so that the first and second slider cams are always forcedslidably toward respective first and second fixing cam sides.

Respective first and second slider cams 41 and 42 are provided with apair of first and second key portions 41 b and 42 b on the outerperiphery, the shaft 30 can be slide in the axial direction by engagingrespective first and second key portions 41 b and 42 b with a first andsecond key grooves 38 d and 40 c provided in the cam cases 38 and 40.

On confronting surfaces of respective first and second fixing cams 33,34 and respective first and second slider cams 41 and 42, first andsecond cam portions 45 and 46 composed of convex portions 45 a, 45 a and46 a, 46 a and concave portions 45 b, 45 b and 46 b, 46 b similarly tothe above-described respective embodiment are provided.

Accordingly, as shown in FIG. 27, FIG. 28 and FIG. 30, by allowing thefirst cam case 38 to insert into and lock at the deformed attachmenthole 3 b provided on the attachment portion 3 a of the display device 3,being the second member, and by allowing the second cam case 40 and thefirst and second cam guides 36, 37 to insert into and lock at thedeformed attachment hole 2 b provided on the attachment portion 2 a ofthe keyboard main body 2, being the first member, the assembling iscompleted.

When the display device 3 is opened and closed with the regard to thekeyboard main body, the first cam case 38 rotates together with theshaft 30 and the first slider cam 41, and the second cam case 40 rotatestogether with the shaft 30 and the second slider cam 42. Then, sincerespective first and second convex portions 45 a and 46 a of respectivefirst and second cam portions 45 and 46 in the closed state of thedisplay device 3 are separated from first and second concave portions 45b and 46 b of respective first and second fixing cam 34 and rotate in apressure contact state with respective flat first and second convexportions 45 a and 46 a of respective first and second cam portions 45and 46 in respective first and second fixing cam 33 and 34, frictiontorque is generated, respective first and second slider cam 41 and 42can stably suspend the display device 3 especially at an open angleabout 100° which is its usage angle. It is of course possible here toopen the display device to 180° with regard to the keyboard main body 2.It is possible to select the friction torque at that time at will byarbitrary selecting the shapes of respective first and second camportions 45 and 46.

When the display device 3 is closed with regard to the keyboard mainbody 2, at just before its closed position (for instance about 10°),since respective first and second convex portions 45 a and 46 ofrespective first and second cam portions 45 and 46 in the first andsecond slider cams 41 and 42 are forced to rotate in the closeddirection when they slide down into respective first and second concaveportions 45 b and 46 b of respective first and second cam portions 45and 46 in respective first and second fixing cam 33 and 34, the displaydevice 3 is closed as if being inhaled naturally even taking the handoff. And in this closed state, the display device 3 is locked to preventitself from opening naturally after closed.

It should be noted that, as another embodiment, the cam case 6 and thecam case 38 can be attached to the attachment portion 2 a on thekeyboard main body 2 side, being the first member, and each of therotation arresting means provided on the outside and inside of the camcases 6, 38, on the outside of the friction case 16, and respectiveoutsides of the fixing cam 10, the slider cams 8, 13, and the cam guides12, 36 and 37 is not limited to the above-described embodiments. It isalso acceptable to be structured that the flange portion of the shaft isprovided in the opposite direction from that in the above-describedembodiments so that the cam cases 6 and 38 are locked with E rings.Further, the shapes of deformed portions, deformed attachment portions,and deformed through holes of respective shafts of the fixing cams andthe fixing members are not limited to those in the embodiments, they canbe formed in various well-known shapes. As for materials used in theshaft, respective cases, the fixing cams, the fixing members and slidercams are not limited to that in the embodiment, material such as SUS,POM, and the like can be used as necessary, though for materials for theshafts, the fixing cams, and the slider cams, it is desirable to usehard material made of metal because strength and abrasion resistance arerequired.

1. A hinge device connecting the attaching portion of a first memberconstituting the keyboard main body and the attaching portion of asecond member constituting the display device, said first member andsaid second member being opened and closed relatively to each other, andsaid hinge device comprised of: a shaft inserted through both of thepair of cam cases provided coaxially and confronting one to the other,while one having a rotation arresting means in the outer circle thereof,and the other not having such rotation arresting means, and said shaftinserted rotatably through both of said cam cases; a pair of cam guides,each one having a rotation arresting means in the outer circle thereof,and thus relocated on the outer surface of said shaft so as to contactimpactedly with each other; a pair of cam mechanisms provided in saidcam case, and fixed between the inner surface thereof and said camguide; and said hinge device comprised of: a pair of fixing cams,wherein such pair of cam mechanisms having cam portion consisting ofconvex portion and depressed portion, and inserting said shaft in thecentral axial direction through each of said cam guides, and thus fixedwith such cam guide; a slider cam having cam portion consisting ofconvex portion and depressed portion at a position confronting to eitherone of said fixing cams, and having said shaft inserted through thecentral portion thereof, and slidable in the axial direction of saidshaft; and a pair of elastic means wound round said shaft in the outercircle thereof, and resiliently provided inside each one of said camcases for pressing each of said slider cam toward said each of fixingcam sides, and; said hinge device, wherein convex portion or depressedportion of either of said cam portions shall be provided plane.
 2. Thehinge device according to claim 1, wherein at least one portion of eachcam portion provided on the fixing cam and the slider cam of each cammechanism is formed in a plane portion so that friction torque isgenerated.